New specificities of the HLA-DRw system will be searched for by cross absorption procedures duo or tri-specific antisera, and using bulk-cultured, previously typed and selected lymphoblastoid cell lines. Reactivities of the sera with donor cells from caucasian, black, oriental, Navajo Indian, and South America Indian subjects will be determined. Dysequilibrium of the HLA system in certain diseases will be investigated: HLA in Alzheimers disease and a number of chromosomal instability syndromes. The possible influence of HLA on DNA-repair processes will be documented.